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Increasing global water shortages are accelerating the pace of membrane manufacturing, which generates many environmentally harmful solvents. Such challenges need a radical rethink of developing innovative membranes that can address freshwater production without generating environmentally harmful solvents. This work utilized the synthesized ultra-long hydroxyapatite (UHA) by the solvothermal method using the green solvent oleic acid in preparing UHA-based forward osmosis membranes. The membranes were developed using different loading ratios of graphene oxide (GO) by vacuum-assisted filtration technique. The prepared GO/UHA membranes were identified using X-ray diffraction, scanning electron microscope, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Water contact angle and pore size distribution were determined for the obtained GO/UHA membranes. The obtained hierarchical porous structure in the prepared membranes with interconnected channels results in a stable water flux with reverse salt flux. The best water flux rate of 42 ± 2 L·m−2·h−1 was achieved using the 50 mg GO/UHA membrane, which is 3.3 times higher than the pristine membrane, and a reverse salt flux of 67 g·m−2·h−1. The obtained results showed a promising capability of a new generation of sustainable inorganic-based membranes that can be utilized in freshwater generation by energy-efficient techniques such as forward osmosis. [ABSTRACT FROM AUTHOR]

The recovery of pure water and valuable substances from wastewater is a major challenge in the context of the circular economy, requiring advanced separation methods. However, actual membrane separation techniques such as forward osmosis are limited by membrane fouling and selectivity. Here, we synthesized composite membranes by crosslinking polyvinyl alcohol hydrogel, using both glutaraldehyde and borax as crosslinking agents, on top of cellulose ester membranes. We tested these composite membranes on model and real wastewater. Results show that the composite membranes retain ammonium effectively, maintain surface electroneutrality, and exhibit remarkable resistance to fouling by organic and biological contaminants. This is explained by the high hydrophilicity of the membrane surface after application of a hydrogel layer. [ABSTRACT FROM AUTHOR]

This study introduces draw solutions for application in forward osmosis (FO) processes, combining mono propylene glycol propyl ether (PGPE) with the cellulose derivative hydroxypropyl cellulose (HPC). A total of 16 unique single‐solute and ternary organic draw solutions were prepared and evaluated, leading to the selection of three promising solutions for further investigation. Notably, eight of the initial organic draw solutions demonstrated osmotic pressures exceeding 2.4 MPa. The dynamic viscosities of all draw solutions exhibited a significant reduction with increasing temperature. Among the investigated solutions, the 0.25HPC‐3.75PGPE demonstrated the most favorable FO performance, achieving average experimental water fluxes of 11.062 and 9.852 Lm−2 h−1 (LMH) against a 1 g/L NaCl brackish feed solution across two FO runs. Practitioner Points: Hydroxypropyl cellulose (HPC, MW ~100,000) was mixed with propylene glycol propyl ether (PGPE) as draw solutes for FO processes.Seven combinations of HPC and PGPE produced osmolalities greater than 1000 mOsm/kg.0.5HPC‐7.5PGPE ternary draw solution achieved experimental water fluxes of 11.062 and 9.852 LMH against 1 g/L NaCl brackish feed solution.Leveraging the LCSTs of these ternary organic solutions holds promise for improved separation and regeneration processes. [ABSTRACT FROM AUTHOR]

Meeting the ever‐increasing need for clean water requires developing highly effective thin‐film nanocomposite (TFN) membranes with outstanding water permeability, selectivity, and good fouling resistance. In this work, ZnO nanoparticles were synthesized and coated with zwitterionic lysine amino acid (ZnO‐lysine) and then incorporated into a polyamide layer to improve their performance as well as to alleviate fouling. The organic shell on the ZnO‐lysine surface promoted the PA layer's interaction with ZnO‐lysine nanoparticles. TFN membranes demonstrated hydrophilic and smooth polyamide layers with improved permeability and selectivity. In particular, the TFN membranes' enhanced hydrophilicity and smooth surface synergized fouling reduction. In comparison to the bare TFC membrane (12.2 LMH) using 1 M NaCl as the draw solution, the ZnO‐lysine‐modified TFN‐ZL.400 membrane (21.1 LMH) yields a water flux that is 75% greater. In the polyamide layer, the zwitterionic functional groups of ZnO‐lysine not only improved the nanoparticles' chemical compatibility, preventing the creation of nonselective gaps, but also enhanced water flux and salt rejection. This study provides insight into the creation of zwitterionic‐functionalized nanoparticles that can successfully address fouling issues and trade‐off restrictions between selectivity and permeability in TFN membranes. [ABSTRACT FROM AUTHOR]

In this work, a dual-pronged approach– (i) novel thin-film nanocomposite polyether sulfone (PES) membrane with MIL-101 (Fe) and (ii) 3D printed spacers were explored to enhance water recovery by forward osmosis. The concentration of PES, pore former, draw solution, and MIL-101(Fe) was optimised for maximum pure water flux (PWF) and minimum specific reverse solute flux (SRSF). The best membrane exhibited a PWF of 7.52 Lm−2 h−1 and an SRSF of 0.33 ± 0.03 gL−1 using 1.5 M NaCl and DI water feed. The M22 membrane with the diamond-type spacer demonstrated a PWF of 2.53 Lm−2 h−1 and SRSF of 0.75 gL−1 for emulsified oily wastewater feed. The novel spacer design imparted significant turbulence to the feed flow and a lower foulant resistance of 1.3 m−1 as compared to the ladder type (1.5 m−1) or commercial spacer (1.7 m−1). This arrangement could recover 19% pure water within 12 h of operation (98% oil rejection) with a ∼ 94% flux recovery after hydraulic wash. [ABSTRACT FROM AUTHOR]

Typically, hydrogels are described as three-dimensional networks of hydrophilic polymers that are able to capture a certain mass of water within their structure. Recently, hydrogels have been widely used as drawing agents in forward osmosis (FO) desalination processes. The major aim of this study is to prepare a novel semi-interpenetrating hydrogel by crosslinking sodium alginate (SA) and polyvinyl alcohol (PVA) by using the epichlorohydrin (ECH) crosslinker and polyethylene glycol (PEG) interpenetrated within the hydrogel's network as a linear polymer. Based on the optimum composition of SA/PVA composite hydrogel obtained from our earlier research, the effect of various percentages of PEG on the response of the hydrogel was investigated. The optimal composition of SA/PVA/PEG hydrogel was characterized by scanning electron microscopy (SEM), compression strength testing, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The morphological and mechanical properties of the SA/PVA/PEG semi-interpenetrating hydrogel were also compared to those of the SA/PVA composite hydrogel. Moreover, the performance of the optimal SA/PVA/PEG hydrogel in a FO batch unit as a drawing agent was investigated based on the optimal operation conditions from our previous experiments. The results showed that the optimal PEG/polymer blend mass ratio was 0.25, which increased the swelling ratio (SR) (%) of the hydrogel from 645.42 (of the neat SA/PVA hydrogel) to 2683. The SA/PVA/PEG semi-interpenetrating hydrogel was superior to the SA/PVA copolymer hydrogel in pore structure and mechanical properties. Additionally, in terms of FO desalination, the achieved water flux by SA/PVA/PEG hydrogel is higher than that accomplished by SA/PVA hydrogel. [ABSTRACT FROM AUTHOR]

Acrylamide is an important chemical in great global demand for the synthesis of polyacrylamide. A facile and benign approach of concentrating high osmotic acrylamide aqueous solution at a low temperature is needed to replace the current energy-intensive and cost-expensive thermal flash evaporation process. For the first time, a multi-stage forward osmosis (FO) process has been developed to concentrate acrylamide solution from 200 g/L to 600 g/L. Thin-film composite (TFC) membrane was fabricated and used for the multi-stage FO process. Acrylamide feed solution (FS) with various concentrations was systematically characterized in terms of viscosity and osmotic pressure (OP). Draw solutes including NaCl and MgCl2 were tested, and their reverse salt fluxes were measured with the quantification of their accumulative contents in the resultant concentrated acrylamide solution. Different operation modes including AL-FS (active layer facing FS) and AL-DS (active layer facing DS) were explored to optimize the system efficiency of the FO concentration process. Both single- and multi-stage FO operations were investigated, and their performances were quantified to assess the efficiency of the concentration of acrylamide solution. The results demonstrate that the multi-stage FO operation could dramatically improve the system efficiency for the concentration of acrylamide solution better than the single-stage FO process, and the draw concentration renewal at Stages II, III, and IV led to a water flux increase of 18.56%, 17.52%, and 18.43%, respectively. Moreover, the accumulated MgCl2 in the final 600 g/L acrylamide solution was below 3.7 g/L, less than 0.62 wt% impurity in the product of acrylamide. Our work provides a practical insight into the viability and optimization of a multi-stage FO process for concentrating high osmotic chemicals. [ABSTRACT FROM AUTHOR]

Recently, alcohol-based draw solute (DS), i.e., alcohol with water, is one of the trending research topics in forward osmosis (FO) because of its performance and ease of regeneration. Nevertheless, the higher reverse solute flux (RSF) of the alcohol-based DS hinders its commercialization in water and wastewater treatment applications. This research aims to minimize the RSF of the alcohol-based DS in FO by investigating the possibility of using alcohol-alcohol-based draw solutes for the first time. Three alcohol-alcohol-based draw solutions, namely, (1) E70 + IPA30 (ethanol: 70% + isopropanol: 30%), (2) E40 + IPA60 (ethanol: 40% + isopropanol: 60%), and (3) E10 + IPA90 (ethanol: 10% + isopropanol: 90%), were prepared and the properties (including osmolality, shear stress, and viscosity) of the DS were first investigated followed by the parametric investigation (concerning temperature and concentration). The results were further analyzed with the fixed-point iterative method in MATLAB to obtain the performance parameters. Results reveal that the E10 + IPA90 mixture yields a lower RSF of 40.62 g/m2/h and specific reverse solute flux of 3.78 g/L with a considerably good water flux and recovery percentage of 11.47 LMH and 26.29%, respectively, as compared to other DS E70 + IPA30 and E40 + IPA60 at 25 °C. Thus, E10 + IPA90 is recommended as a potential candidate to be used as a DS in FO. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) is a membrane process of water separation and purification. FO uses the osmotic pressure difference across a semipermeable membrane. The effective osmotic pressure at the membrane–solution interface on both the feed and permeate sides of the membrane is the main driving force for the generation of the water flux. The major hindrance to the permeation of the water flux is the prevalence of concentration polarization on both sides of the membrane. Concentration polarization inhibits permeate flux by increasing the osmotic pressure at the membrane active layer interface on the feed side of the membrane. This work focused on the development of a mathematical model for water flux in the FO process. Combined film theory model and diffusion transport through the membrane were utilized. The effect of internal concentration polarization and external concentration polarization on the flux was studied. Both internal and external concentration polarization were taken into consideration in both membrane orientations, i.e., active layer facing the feed solution and active layer facing the draw solution. The obtained explicit expression for water permeation flux in forward osmosis desalination process shows excellent agreement with the literature data. [ABSTRACT FROM AUTHOR]

The growing interest in forward osmosis (FO) for water reclamation and desalination over the past two decades stems from its potential for lower energy consumption. Despite its promise, FO faces significant challenges, such as the lack of an appropriate draw solute, concentration polarization, membrane fouling, and reverse solute flux (RSF). Recent trends in research have focused on combining various technologies with FO to address these challenges. Notably, the integration of electrochemical technologies with FO offers new possibilities. This review covers FO combined with electrochemical cells (FO‐ECs), categorizing them based on their working principles and applications in improving FO. The review discusses different FO‐EC configurations, including (1) electrodialysis‐combined FO for RSF, (2) electro‐FO for water flux enhancement, and (3) electrochemical oxidation‐combined FO and FO with electro‐conductive membranes for self‐cleaning and fouling mitigation. Additionally, it covers (4) reusable electro‐responsive draw solutes, (5) electrochemical osmosis systems for metal removal and energy production, and (6) osmotic microbial fuel cells for energy recovery and other benefits. The review also assesses the practical applicability and potential for achieving carbon neutrality of the FO‐ECs. It concludes with a forward‐looking perspective, outlining future research directions to optimize and expand the use of electrochemical‐enhanced FO technologies. [ABSTRACT FROM AUTHOR]

The agricultural sector uses 70% of the world's freshwater. As clean water is extracted, groundwater quality decreases, making it difficult to grow crops. Brackish water desalination is a promising solution for agricultural areas, but the cost is a barrier to adoption. This study investigated the performance of the fertilizer drawn forward osmosis (FDFO) process for brackish water desalination using response surface methodology (RSM) and artificial neural network (ANN) approaches. The RSM model was used to identify the optimal operating conditions, and the ANN model was used to predict the water flux (Jw) and reverse solute flux (Js). Both models achieved high accuracy, with RSM excelling in predicting Js (R2 = 0.9614) and ANN performing better for Jw (R2 = 0.9801). Draw solution (DS) concentration emerged as the most critical factor for both models, having a relative importance of 100% for two outputs. The optimal operating conditions identified by RSM were a DS concentration of 22 mol L−1, and identical feed solution (FS) and DS velocities of 8.1 cm s−1. This configuration yielded a high Jw of 4.386 LMH and a low Js of 0.392 gMH. Furthermore, the study evaluated the applicability of FDFO for real brackish groundwater. The results confirm FDFO's potential as a viable technology for water recovery in agriculture. The standalone FO system proves to be less energy-intensive than other desalination technologies. However, FO exhibits a low recovery rate, which may necessitate further dilution for fertigation purposes. [ABSTRACT FROM AUTHOR]

Abstract Typically, hydrogels are described as three-dimensional networks of hydrophilic polymers that are able to capture a certain mass of water within their structure. Recently, hydrogels have been widely used as drawing agents in forward osmosis (FO) desalination processes. The major aim of this study is to prepare a novel semi-interpenetrating hydrogel by crosslinking sodium alginate (SA) and polyvinyl alcohol (PVA) by using the epichlorohydrin (ECH) crosslinker and polyethylene glycol (PEG) interpenetrated within the hydrogel’s network as a linear polymer. Based on the optimum composition of SA/PVA composite hydrogel obtained from our earlier research, the effect of various percentages of PEG on the response of the hydrogel was investigated. The optimal composition of SA/PVA/PEG hydrogel was characterized by scanning electron microscopy (SEM), compression strength testing, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The morphological and mechanical properties of the SA/PVA/PEG semi-interpenetrating hydrogel were also compared to those of the SA/PVA composite hydrogel. Moreover, the performance of the optimal SA/PVA/PEG hydrogel in a FO batch unit as a drawing agent was investigated based on the optimal operation conditions from our previous experiments. The results showed that the optimal PEG/polymer blend mass ratio was 0.25, which increased the swelling ratio (SR) (%) of the hydrogel from 645.42 (of the neat SA/PVA hydrogel) to 2683. The SA/PVA/PEG semi-interpenetrating hydrogel was superior to the SA/PVA copolymer hydrogel in pore structure and mechanical properties. Additionally, in terms of FO desalination, the achieved water flux by SA/PVA/PEG hydrogel is higher than that accomplished by SA/PVA hydrogel.

Abstract Forward osmosis (FO) is a membrane process of water separation and purification. FO uses the osmotic pressure difference across a semipermeable membrane. The effective osmotic pressure at the membrane–solution interface on both the feed and permeate sides of the membrane is the main driving force for the generation of the water flux. The major hindrance to the permeation of the water flux is the prevalence of concentration polarization on both sides of the membrane. Concentration polarization inhibits permeate flux by increasing the osmotic pressure at the membrane active layer interface on the feed side of the membrane. This work focused on the development of a mathematical model for water flux in the FO process. Combined film theory model and diffusion transport through the membrane were utilized. The effect of internal concentration polarization and external concentration polarization on the flux was studied. Both internal and external concentration polarization were taken into consideration in both membrane orientations, i.e., active layer facing the feed solution and active layer facing the draw solution. The obtained explicit expression for water permeation flux in forward osmosis desalination process shows excellent agreement with the literature data.

In this study, a multi-functional layer was developed based on the commercially available cellulose triacetate (CTA) forward osmosis (FO) membrane to improve its antifouling property. Tannic acid/ferric ion (TA/Fe3+) complexes were firstly coated as a precursor layer on the membrane surface via self-assembly. Afterwards, the tannic acid/diethylenetriamine (TA/DETA) hydrophilic functional layer was further coated, following Ag/polyvinylpyrrolidone (PVP) anti-bacterial layer was formed in situ through the reducibility of TA to obtain TA/Fe3+-TA/DETA-Ag/PVP-modified membrane. The optimized precursor layer was acquired by adjusting the buffer solution pH to 8, TA/Fe3+ ratio to 4 and the number of self-assembled layers to 5. The permeability testing results illustrated that the functional layer had an insignificant effect on the membrane transport parameters. The TA/Fe3+-TA/DETA-Ag/PVP-modified membrane simultaneously exhibited excellent physical and chemical stability. The coated membrane also demonstrated enhanced anti-bacterial properties, achieving 98.63 and 97.30% inhibition against Staphylococcus aureus and Escherichia coli, respectively. Furthermore, the dynamic fouling experiment showed a 12% higher water flux decrease for the TA/Fe3+-TA/DETA-Ag/PVP CTA membrane compared to the nascent CTA membrane, which proved its excellent antifouling performance. This work provides a feasible strategy to heighten the antifouling property of the CTA FO membrane. HIGHLIGHTS Surface modification of CTA FO through TA/Fe3+ and TA/DETA coating layers and in situ reduction of Ag.; The multi-functional layer had no considerable impact on the mass transport coefficients of the CTA FO membrane.; The antifouling of the modified membrane was remarkably improved for raw municipal wastewater treatment.;

Abstract Recently, hydrogels have been widely applied as draw agents in forward osmosis (FO) desalination. This work aims to synthesize bioartificial hydrogel from a blend of sodium alginate (SA) and polyvinyl alcohol (PVA) using epichlorohydrin (ECH) as a crosslinker. Then this prepared hydrogel was applied as a draw agent with cellulose triacetate membrane in a batch (FO) cell. The effects of the PVA content in the polymer blend and the crosslinker dose on the hydrogel’s swelling capacity were investigated to optimize the hydrogel’s composition. Furthermore, the water flux and the reverse solute flux of the optimum SA/PVA hydrogel were evaluated in a batch (FO) unit under the effect of the hydrogel’s particle size, feed solution (FS) temperature, FS concentration, and membrane orientation. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and compression strength tests were used to characterize the prepared hydrogel. Results revealed that the equilibrium swelling ratio (%) of 5228 was achieved with a hydrogel that had 25% PVA and a crosslinking ratio of 0.8. FO experiments revealed that the maximum water flux of 0.845 LMH achieved, when distilled water was used as FS, average hydrogel’s particle size was 60 µm, and the FS temperature was 40 °C.

The forward osmosis (FO) process has recently gained significant interest in treating wastewater, brackish/seawater and concentrating feedstocks for various operations, including desalination. The study investigates the effect of different synthesis conditions of the polyamide-based thin-film composite (TFC) FO membranes on the membranes' final performance. Taguchi statistical analyses were used to fabricate and optimize the polyamide TFC FO membrane. The process parameters as factors were the amount of polyethersulfone (PES), polyethylene glycol 400 (PEG-400), polyvinyl pyrrolidone (PVP), m-phenylenediamine (MPD), and trimesoyl chloride (TMC), and TMC reaction-time (RT). The Taguchi method was adopted to investigate the optimal conditions and the significance of individual factors using an L16 (45) orthogonal array. Another Taguchi analysis (Taguchi 2) was adopted to investigate the influence of other important parameters like optimal conditions for MPD, TMC, and TMC reaction-time factors using an L9 (33) orthogonal array. Confirmation tests validated a maximum water flux of 46.4 ± 2.32 L/m2·h with a specific combination of control factors for membrane synthesis: PES/PEG/PVP/MPD/TMC/TMC RT-16/7/0.5/1/0.05/30. These tests demonstrated a high-water flux of 7.05 ± 0.35 L/m2·h when exposed to industrial wastewater (secondary effluent) as the feed solution (FS) and fertilizer as the draw solution (DS) in the FO process. The R2 values were more than 90%. The experimental validation confirmed the models' predictive ability with different FSs, including industrial wastewater. [ABSTRACT FROM AUTHOR]

The current study focuses on the efficiency of the fertilizer-drawn forward osmosis process to produce a nutrient solution for hydroponic use. Instead of separating the draw solution from desalinated water, this study explores the potential of using the diluted fertilizer draw solution directly for fertigation. To achieve this, different fertilizers were tested as draw solutions. The study tested eight single inorganic and one organic salt separately and mixtures of these salts. Two parameters, water flux and reverse salt flux, were used to evaluate the forward osmosis process. The results indicate that mixed salts have a higher water flux than single salts due to increased draw solution osmotic pressure. In contrast, mixed salts have a lower reverse salt flux than single salts. The reverse salt flux varied from 17.42 g/m2.h for KCl to 5.15 g/m2.h for Mg(C2H3O2)2·4H2O. The water flux of the single salts ranged from 2.44 L/m2.h for Mg(C2H3O2)2·4H2O to 4.47 L/m2.h for MgCl2·6H2O. The mixture of NaNO3 and Mg(C2H3O2)2·4H2O gave the highest water flux at 5.92 L/m2.h; while, the mixture of MgCl2·6H2O and Mg(C2H3O2)2·4H2O produced the lowest reverse salt flux. [ABSTRACT FROM AUTHOR]

Thermally responsive polymers (TRPs) have gained significant attention in the past decade due to their unique phase transition behavior, those exhibiting changes in properties with temperature variations. In water, hydrophilic block copolymers form helical structures that can transform into hydrophobic globules above the lower critical solution temperature (LCST). Fouling is one of the limiting issues for the forward osmosis (FO) process in wastewater treatment. In this work, after the treatment of wastewater from the paper and pulp industries, foulants were removed from the surface of the commercial polyamide thin‐film composite membrane of the FO process using polyvinyl methyl ether (PVME), a TRP with an LCST of 35–37°C. PVME was mixed with different aqueous solutions to form cleaning solutions. Foulant cleaning experiments utilized a 1% PVME (w/v) solution in 300 mL of de‐ionized (DI) water, while 1 M NaCl solution served as the draw solution (DS) in the FO process. Comparing the water flux (J) and change in membrane hydraulic resistance (Rf) among pristine, fouled, and cleaned membranes revealed a 56.67% increase in water flux and a 51.68% decrease in membrane resistance after PVME mixed with DI water cleaning solution showcasing its effectiveness in improving membrane performance and reducing fouling. The cleaning efficiency of two solutions, that is, 1% PVME mixed in DI water and 1% PVME mixed in 1 M aqueous urea solution, is compared. Results showed that the former cleaning solution helped to obtain 32.62% higher water flux and 56.05% less membrane resistance. Various membrane characterizations are performed, such as field emission scanning electron microscopy (FE‐SEM), which characterizes the membrane's pore structure and surface morphology, while a contact angle analyzer assesses hydrophilicity. This research highlights the use of TRPs as effective cleaning agents, enhancing membrane performance by effectively removing foulants on the membrane surface. Investigating alternative cleaning solutions also provides insights for optimizing water treatment processes. Highlights: Cleaning of fouled thin‐film composite membrane using thermal‐responsive polymers (TRPs).Polyvinyl methyl ether, a TRP with an lower critical solution temperature of 35–37°C used as a cleaning agent.60% increase in water flux was observed after the single‐step cleaning process.Multiple uses of TRP for cleaning performed with no membrane damage. [ABSTRACT FROM AUTHOR]

Modification of membranes is widely used for altering their separation properties. In this study, the modification of PVDF nanofiber mat by deposition of polyamide layers was evaluated to improve dye recovery by means of forward osmosis process. The polyamide active layer was prepared by a reaction of cyclic aromatic amines, m-phenylenediamine, or piperazine, and trimesoylchloride. The modification progress was monitored by FTIR analysis, water uptake, nitrogen content, and grafting yields. Investigated membranes showed an excellent dye separation features with water flux and dye fluxes strongly related to type of applied amines and reaction time. The best obtained membrane demonstrated outstanding performance in forward osmosis; their water flux was 3.3 LMH and rejection rate of 97% for bromocresol green dye. The membrane allowed increase dye concentration by 50% after 24 h of the process. [ABSTRACT FROM AUTHOR]

In the present study, poly acrylonitrile (PAN) nanofiltration membrane has been tailored for applying in forward osmosis (FO) process via the combination of two modification approaches including blending and layer-by-layer (LBL)-surface modification techniques. Firstly, dopamine was embedded in PAN nanofiltration membrane to improve its hydrophilicity and antifouling features so that at the optimal loading rate (0.1 wt%) water contact angle (WCA) of the bare membrane declined from 62.7° to 54.5°, its pure water flux augmented from 3.59 to 7.2 kg/m2 h, and its flux recovery ratio (FRR) increased from 70.6 to 92.3%. Secondly, LBL technique has been performed on the optimal MM membrane's surface (with 0.1 wt%) by using poly diallyl dimethyl ammonium and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt as poly cation and poly anion, respectively. From the obtained results, the insertion of 5 bilayers on the optimally dopamine–incorporated membrane's surface showed an outperformance compared to the others with FRR and WCA of 99.2% and 34.5°, respectively. Finally, the performances of the synthesized membranes were evaluated in a FO setup containing NaCl (1M) as a draw solution and deionized water as a feed solution. Pursuant to the obtained results, the optimally tailored membrane by using both the modification methods revealed the lowest reverse solute flux (3.9 g/m2 h) and a moderate pure water flux (3 l/m2 h), corroborating its potential to be used in an effectual FO process. [ABSTRACT FROM AUTHOR]

This study investigates how temperature and forward osmosis (FO) membrane properties, such as water permeability (A), solute permeability (B), and structural parameter (S), affect the specific energy consumption (SEC) of forward osmosis-reverse osmosis system. The results show that further SEC reduction beyond the water permeability of 3 LMH bar-1 is limited owing to high concentration polarization (CP). Increasing S by 10-fold increases FO recovery by 177.6%, causing SEC decreases by 33.6%. However, membrane with smaller S also increases external CP. To reduce SEC, future work should emphasize mixing strategies to reduce external CP. Furthermore, increasing the temperature from 10 to 40 °C can reduce SEC by 14.3%, highlighting the energy-saving potential of temperature-elevated systems. The factorial design indicates that at a lower temperature, increasing A and decreasing S have a more significant impact on reducing SEC. This underlines the importance of developing advanced FO membranes, particularly for lower-temperature processes. [ABSTRACT FROM AUTHOR]

In this study, a facile method for multifunctional surface modification on forward osmosis (FO) membrane was constructed by surface immobilization of AgNPs based on tannic acid (TA)/diethylenetriamine (DETA) precursor layer. The cellulose triacetate (CTA) FO membranes modified by TA and DETA with different co-deposition time (6 h, 12 h, 24 h) were investigated. Results indicated that the TA/DETA (24)-Ag CTA membrane with a TA/DETA co-deposition time of 24 h was identified to be optimal, which attained more hydrophilic. And it had the bacterial mortality of Escherichia coli and Staphylococcus aureus reaching 98.23% and 99.83% respectively and possessed excellent physical and chemical binding stability. Meanwhile, the coating layer resulted in the antifouling ability without damaging the membrane intrinsic transport characteristics. As for synthetic municipal wastewater treatment, the water flux of CTA FO membrane decreased approximately 49% of the initial flux after running for 14 days. In contrast, the flux decline rate of TA/DETA (24)-Ag CTA membrane was about 37%. Furthermore, less foulant deposition and higher recovery rate of water flux was observed for TA/DETA (24)-Ag CTA membrane, implying that the modified membrane effectively alleviated membrane fouling and processed a lower flux decline during municipal wastewater treatment. It was attributed to the enhanced surface hydrophilicity and antibacterial property of the coating layer, which improved antifouling property. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) has emerged as a new star in the family of membrane-based separation processes not only as a stand-alone system for high-fouling feed but also in combination with other membrane processes. In spite of being a non-pressurized process, their widespread commercial applications compared to classical technologies are still constrained by core challenges, primarily low flux, concentration polarization, energy-intensive draw, and solute recovery. Carbon Quantum dots (CQDs) - an emerging class of carbon-based smart nanomaterials has stimulated a renewed interest in FO research for membrane as well as draw solutes development. Given the general panorama of past-to-present literature, the paper intends to provide a comprehensive survey on the CQD synthesis and their various modes of incorporation into FO membranes for process improvement. Thin film nanocomposites and active skin layers modification by incorporation of CQDs, via phase inversion or interfacial polymerization, were attempted by researchers and compared to other techniques. Although CQD incorporation resulted in appreciable water flux improvements, the reverse solute flux remains a concern. The uses of CQDs, both as a pristine and functionalized version, prove to be promising as a valuable ingredient of draw solute for the FO process. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) has become an attractive option to produce potable water to cater the global needs. Despite the potential advantages of the RO process, it has limitations too. To address such limitations membrane distillation (MD), forward osmosis (FO) and pressure-retarded osmosis (PRO) are now becoming emerging areas of research for seawater desalination. With significant advances in FO and MD for desalination, the entire operation to be conducted at low hydraulic pressure, which reduces fouling and improves membrane life. PRO is an osmotically driven process that produces green energy from the brine stream. However, hybrid desalination processes in combination with RO, are found to be efficient compared to stand-alone technology, with a reduced desalination cost. Although a few studies are available, practical integration of the current state of the art and its gradual progress is rarely addressed. In this context, emerging FO, MD, PRO processes, and the development of membranes for energy minimisation with improved performance are presented herein. Hybrid processes in combination with renewable energy resources are evaluated. Significant technological development and emergence of new materials is anticipated to play a pivotal role so that membrane-based desalination technologies become more efficient and economical in near future. [ABSTRACT FROM AUTHOR]

Promising forward osmosis (FO) membrane desalination is a potentially viable energy‐efficient performance technology compared to other techniques. Searching for the ideal draw solute that creates high osmotic pressure difference and ease of regeneration is critical for water desalination using the FO system. However, many fundamental aspects still need to be adapted, such as needing more screening potential anions and cations based on the predictive method. The Group Contribution Method (GCM) was used in this study to predict the value of the van't Hoff factor denoted by (i). In the end, 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([C4C1im][BF4]) was selected as a draw solution for later experimental work. [ABSTRACT FROM AUTHOR]

Composite membranes constructed using both graphene oxide and carbon nanotubes (CNTs) were designed to strengthen the forward osmosis (FO) technology for the removal of organic contaminants. The nano-membrane was chemically treated with organic acids, which were citric acid in this case for more efficiency in permeability and pollutant removal. The efficiency of the composite membranes in organic pollutants removal was estimated by checking the levels of COD (chemical oxygen demand), TKN (total nitrogen analysis), and (TOC) organic carbon in the water sample before and after applying the technology. The analysis of the study recommends that the nano-membranes may be appropriately used to reduce organic pollutants significantly, to 98.20% efficiency, in addition to elevating water quality standards. This was caused by the higher degree of selectivity and permeability of the membranes that was consequent to the treatment of the organic acid. In brief, the employment of citric acid in the pre-treatment procedures for the preparation of composite graphene oxide-carbon nanotube membranes for FO technology could take water cleaning technologies a step ahead toward sustainable technology. The application of the composite membrane with graphene oxide and carbon nanotubes is not only efficient in cleaning out organic contaminants but it has a lot of added benefits. These membranes are easily manufactured with a long lifespan which, in turn, makes them cost-effective and environmentally friendly. Also, forward osmosis technology reduces the energy demand compared to other water remediation methods, making it a more sustainable solution. The final point of this article is that the using of composite graphene oxide-carbon nanotube membranes treated with an organic acid, such as citric acid, in FO technology not only assists with the water treatment problem but also elevates sustainablility due to its effectiveness and is environmentally friendly. [ABSTRACT FROM AUTHOR]

Thin-film nanocomposite (TFN) forward osmosis (FO) membranes have attracted significant attention due to their potential for solving global water scarcity problems. In this study, we investigate the impact of titanium oxide (TiO2) and titanium oxide/reduced graphene (TiO2/rGO) additions on the performance of TFN-FO membranes, specifically focusing on water flux and reverse salt diffusion. Membranes with varying concentrations of TiO2 and TiO2/rGO were fabricated as interfacial polymerizing M-phenylenediamine (MPD) and benzenetricarbonyl tricholoride (TMC) monomers with TiO2 and its reduced graphene composites (TiO2/rGO). The TMC solution was supplemented with TiO2 and its reduced graphene composites (TiO2/rGO) to enhance FO performance and reverse solute flux. All MPD/TMC polyamide membranes are characterized using various techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. The results demonstrate that incorporating TiO2/rGO into the membrane thin layer improves water flux and reduces reverse salt diffusion. In contrast to the TFC membrane (10.24 L m−2h−1 and 6.53 g/m2 h), higher water flux and higher reverse solute flux were detected in the case of TiO2and TiO2/rGO-merged TFC skin membranes (18.81 and 24.52 L m−2h−1 and 2.74 and 2.15 g/m2 h, respectively). The effects of TiO2 and TiO2/rGO stacking on the skin membrane and the performance of TiO2 and TiO2/rGO skin membranes have been thoroughly studied. Additionally, being investigated is the impact of draw solution concentration. [ABSTRACT FROM AUTHOR]

The thin film composite (TFC) membrane possesses the highest commercial application potential among all types of forward osmosis (FO) membranes. The support layer of the membrane plays a crucial role in both bearing mechanical loads and facilitating the active layer formation. Herein, we addressed the issues of low permeability and poor mechanical strength of the conventional TFC FO membrane by selecting suitable fabrics and optimizing membrane design and preparation. Polyester (PS) woven fabric, with its high strength, low thickness, and high porosity, served as an excellent material for reinforcing the strength of the FO membrane. We employed a novel double-blade casting method to address the defect issue associated with the conventional single-blade casting method. The influencing factors and quality control strategies of the fabric-reinforced substrate were systematically investigated. Furthermore, membrane characterization techniques, including scanning electron microscopy (SEM), liquid-liquid displacement porometer, and cross-flow FO system, were used to reveal the influences of different substrates, including polysulfone (PSU), polyacrylonitrile (PAN), and polyetherimide (PEI), on the structure and performance of the fabric-reinforced TFC-FO membrane. Compared to commercial FO membranes, the TFC/PSU membrane exhibited superior FO performance, with a water flux of 24.1 LMH, and outstanding mechanical strength that was more than 10-times higher than that of free-standing membranes. This study demonstrates a new pathway for engineering robust TFC-FO membranes with low structural parameters as well as excellent scalability of the membrane fabrication method.

In order to carry out osmotic purification of black and odorous water and solve the problems of low water flux, reverse solute diffusion and biological pollution affecting the forward osmosis performance, the author proposed the application of graphene nickel oxide nanocomposites in the treatment of black and odorous water. The hydrophilic metal-organic framework (UiO-66 nanoparticle) is embedded into the lamellar structure of graphene nickel oxide as a microporous filler, form ultra-thin “sandwich” film to improve FO performance. The added UiO-66 nano-particles introduce a uniform and suitable nano-channel, which can effectively let water penetrate, at the same time, block the reverse diffusion of Na+. The results show that the film with nanometer thickness formed by GO layer can prevent biological pollution, and the bacteriostatic effect can reach 90 %. In the FO model, the water flux of UiO-66/GO membrane is 29.16 LMH, which is 270 % higher than the original pure graphene nickel oxide membrane, and the reverse solute diffusion is 83.5 % lower (12.86 gMH). It is proved that this study provides an attempt for the application of MOF/GO film in FO process. Combining the excellent overall performance of UiO-66/GO film and the designable features of MOF structure, we expect that MOF/GO film will have broad application prospects as an advanced membrane material of FO technology.

Abstract The growing interest in forward osmosis (FO) for water reclamation and desalination over the past two decades stems from its potential for lower energy consumption. Despite its promise, FO faces significant challenges, such as the lack of an appropriate draw solute, concentration polarization, membrane fouling, and reverse solute flux (RSF). Recent trends in research have focused on combining various technologies with FO to address these challenges. Notably, the integration of electrochemical technologies with FO offers new possibilities. This review covers FO combined with electrochemical cells (FO‐ECs), categorizing them based on their working principles and applications in improving FO. The review discusses different FO‐EC configurations, including (1) electrodialysis‐combined FO for RSF, (2) electro‐FO for water flux enhancement, and (3) electrochemical oxidation‐combined FO and FO with electro‐conductive membranes for self‐cleaning and fouling mitigation. Additionally, it covers (4) reusable electro‐responsive draw solutes, (5) electrochemical osmosis systems for metal removal and energy production, and (6) osmotic microbial fuel cells for energy recovery and other benefits. The review also assesses the practical applicability and potential for achieving carbon neutrality of the FO‐ECs. It concludes with a forward‐looking perspective, outlining future research directions to optimize and expand the use of electrochemical‐enhanced FO technologies.

Abstract Recently, fresh water resources have been limited globally. Thus, desalination has been the most recommended solution to overcome this issue. Forward osmosis (FO) is an affordable and developing desalination technique. In this current study, a cutting-edge green hydrogel was prepared from a polymer blend of flaxseed gum (FG) and sodium alginate using epichlorohydrin (ECH) as a crosslinker and polyethylene glycol (PEG) as a semi-interpenetrating network polymer. The impact of PEG incorporation on the hydrogel’s response was investigated, and the influence of different mass contents of FG and ECH on the swelling measurements of the hydrogel was studied to optimize the composition of the hydrogel. The optimum hydrogel was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction and the compressive strength test. Furthermore, the behavior of the present hydrogel was examined as a draw agent in a batch FO unit. The water flux and the reverse solute flux were measured at various values of average hydrogel particle size and feed solution (FS) temperature and concentration. The optimal hydrogel of 0.3 PEG/polymer blend mass ratio, 12% FG, and 0.95 ECH/polymer blend mass ratio exhibits a swelling ratio (%) of 1800 after an hour and an equilibrium swelling ratio (ESR) (%) of 5300. The results of the FO experiments revealed that raising FS temperature and reducing FS concentration and average hydrogel particle size enhance water flux.

To evaluate the potential of Na-ZSM-5 membrane for liquid food concentration, the concentration of fruit juice by a tubular Na-ZSM-5 membrane was demonstrated in forward osmosis operation. Apple, orange, and pineapple juices were successfully concentrated, maintaining their quality without contamination by a draw solution based on a molecular sieving effect of the zeolite membrane. For example, the sugar content of apple juice increased from 10.7 to 17.1 oBrix after 24 h of dehydration. The fouling resistance of Na-ZSM-5 membrane was evaluated using a 10 g L-1 pectin solution and cellulose suspension. Na-ZSM-5 membrane showed stable dehydration performance for fruit juice concentration over 120 h without fouling due to pectin or cellulose. In addition, the membrane exhibited high heat resistance, with no deterioration up to 353 K. We showed that Na-ZSM-5 membrane is a potential material for fruit juice concentration because of its superior heat, acidity, and fouling resistances.

This work developed a novel approach to the in‐situ synthesis of ZnO nanoparticles to modify the polysulfone (PSf) porous membrane substrate. The zinc acetate was added to the casting solution, and ZnO nanoparticles were synthesized during phase inversion. The non‐solvent pH and zinc acetate concentration controlled the ZnO synthesis and loading. Their effect on the substrates properties in terms of morphology, hydrophilicity and porosity was studied thoroughly. The result shows that the ZnO nanoparticles was not formed in acidic pH, while ZnO nanoparticles with size of 20 nm could be easily formed in basic pH. The successful synthesis of ZnO nanoparticles was investigated using FTIR and EDX analysis. The EDX images verify that in‐situ synthesis led to a more uniform dispersion than conventional incorporation method. Then the effect of ZnO loading on the interfacial reaction and polyamide (PA) structure was investigated. SEM images verify the successful synthesis of a uniform and defect‐free PA thin film on ZnO modified substrates. FO performance results show an enhancement in water flux and salt rejection as a result of ZnO incorporation in thin film nanocomposite (TFN) membranes, where TFN 1 wt.% in‐situ membrane showed 40% higher water flux than the control TFC membrane. The porous and hydrophile substrate in TFN 1 wt.% in‐situ membrane is responsible for improved separation performance. These modified membranes displayed uniform dispersion of ZnO nanoparticles within substrates, confirming that this method could effectively restrain the aggregation of the nanoparticles. [ABSTRACT FROM AUTHOR]

Classical purification of pharmaceuticals is energy-intensive and employs toxic solvents that are discarded, calling for more sustainable methods. Here, we purified tetracycline by organic solvent forward osmosis using ionic liquids. Results show the osmotic enrichment of feed solutions containing different concentrations of tetracycline in methanol. The solvent flux during the filtration process is mainly influenced by solvent properties, such as molecular size, viscosity, polarity, and the solvent–membrane interaction. We evaporated the diluted draw solution to recover the draw solute for reuse. Overall ionic liquids appear as suitable draw solutes for organic solvent forward osmosis for pharmaceutical compound enrichment with draw solute recovery and reuse. [ABSTRACT FROM AUTHOR]

Recently, fresh water resources have been limited globally. Thus, desalination has been the most recommended solution to overcome this issue. Forward osmosis (FO) is an affordable and developing desalination technique. In this current study, a cutting-edge green hydrogel was prepared from a polymer blend of flaxseed gum (FG) and sodium alginate using epichlorohydrin (ECH) as a crosslinker and polyethylene glycol (PEG) as a semi-interpenetrating network polymer. The impact of PEG incorporation on the hydrogel's response was investigated, and the influence of different mass contents of FG and ECH on the swelling measurements of the hydrogel was studied to optimize the composition of the hydrogel. The optimum hydrogel was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction and the compressive strength test. Furthermore, the behavior of the present hydrogel was examined as a draw agent in a batch FO unit. The water flux and the reverse solute flux were measured at various values of average hydrogel particle size and feed solution (FS) temperature and concentration. The optimal hydrogel of 0.3 PEG/polymer blend mass ratio, 12% FG, and 0.95 ECH/polymer blend mass ratio exhibits a swelling ratio (%) of 1800 after an hour and an equilibrium swelling ratio (ESR) (%) of 5300. The results of the FO experiments revealed that raising FS temperature and reducing FS concentration and average hydrogel particle size enhance water flux. [ABSTRACT FROM AUTHOR]

Polyethylene glycol (PEG) and amphiphilic PEG-block-polysulfone-block-PEG (PEG-b-PSU-b-PEG) triblock copolymer were prepared to modify the substrate of the thin film composite (TFC) membrane. The effects on the physical and chemical properties, structure, and separation performances of the membrane were investigated. The PEG-b-PSU-b-PEG modified substrate was not conducive to the formation of the high-quality active layer by interfacial polymerization (IP), although the substrate hydrophilicity was improved. The forward osmosis (FO) performances of the membrane were worse than those of the unmodified membrane. In contrast, the PEG modified membrane exhibited superior performances. The water flux (Jw) was 22.29 LMH using 1 M NaCl draw solution (DS), corresponding to a notable increase of 23.3% than that of the unmodified membrane. The specific reverse salt flux (Js/Jw) was as low as ~ 0.1 g/L. The direct incorporation of PEG was a more effective and simple strategy for the substrate modification, compared with PEG-b-PSU-b-PEG. For the first time, this study reports the adverse effect of hydrophilicity on the TFC-FO membrane performance. [ABSTRACT FROM AUTHOR]

As an emerging desalination technology, forward osmosis (FO) can potentially become a reliable method to help remedy the current water crisis. Introducing uncomplicated and precise models could help FO systems' optimization. This paper presents the prediction and evaluation of FO systems' membrane flux using various artificial intelligence‐based models. Detailed data gathering and cleaning were emphasized because appropriate modeling requires precise inputs. Accumulating data from the original sources, followed by duplicate removal, outlier detection, and feature selection, paved the way to begin modeling. Six models were executed for the prediction task, among which two are tree‐based models, two are deep learning models, and two are miscellaneous models. The calculated coefficient of determination (R2) of our best model (XGBoost) was 0.992. In conclusion, tree‐based models (XGBoost and CatBoost) show more accurate performance than neural networks. Furthermore, in the sensitivity analysis, feed solution (FS) and draw solution (DS) concentrations showed a strong correlation with membrane flux. Practitioner Points: The FO membrane flux was predicted using a variety of machine‐learning models.Thorough data preprocessing was executed.The XGBoost model showed the best performance, with an R2 of 0.992.Tree‐based models outperformed neural networks and other models. [ABSTRACT FROM AUTHOR]

Controlling the internal concentration polarization in forward osmosis (FO) membranes by minimizing the substrate thickness is critical to enhancing the water flux. This study aimed to achieve the fabrication of an ultra-thin FO membrane by forming the polyamide (PA) active layer on a thin and straight-bore film, a so-called track-etched (TE) membrane. The polycarbonate TE membrane had a uniform pore size of 0.22 µm and a thickness of 25 µm. The PA active layer was successfully formed only by creating a thin m-phenylenediamine solution layer on the smooth TE membrane surface before interfacial polymerization. The TE- FO membrane with low porosity (14 %) provided a water flux of 21 L/m2h and a reverse salt flux of 8.0 g/m2h when evaluated with a 1.0 M NaCl draw solution. Further evaluations showed the potential of increasing water flux by increasing the TE substrate porosity (14 %) and reducing the apparent PA active layer thickness (504 nm). These results suggest the potential of achieving a high-water flux FO membrane using a thin TE substrate and ultimately improving the validity of FO membrane-based water treatment.

The performances of polybenzimidazole (PBI) and polysulfone (PSF) membranes for recovering water from reverse osmosis (RO) reject of brackish water through forward osmosis (FO) were assessed and compared. Non-functionalised multi-walled carbon nanotubes (MWCNT) were added to the membrane casting solutions, with concentrations ranging from 0 to 3 wt%. The experiment was conducted for eight samples using RO reject of brackish water as the feed solution (FS) and 2 M analytical grade MgCl2 as the draw solution (DS). The hydrophilicity, water permeability, salt rejection rate (Rs), water flux (WF) and porosity of the membranes improved with increasing MWCNT content up to 2 wt%. Also, the structural parameter, salt permeability and reverse solute flux decreased. PBI/MWCNT2 wt% exhibited the best performance among the membranes tested compared with porosity of 70 ± 4 %, structural parameter of 0.36 ± 0.2 μm, and Rs of 93.5 %. In contrast with the pristine PBI membrane, an average water flux enhancement of 15 % and 49 % was observed for the FS and DS sides, respectively, for PBI/MWCNT2 wt%. It is evident from the results that including MWCNT improves the performance of both membranes, with better relative performance for PBI membranes than PSF membranes.

Sustainable water recovery and reuse are critical yet challenging, especially from industrial effluents in cold regions. This work presents a robust numerical model of the transport phenomena in a hybrid two-step forward osmosis (FO)-directional freeze crystallization (DFC) desalination process, whose application in areas with cold climates is advantageous. Deionized (DI) water and a hydrometallurgical effluent were considered as the feed solution in the FO step, while three aqueous solutions of inorganic salts were considered as the draw solutions (DS): NaCl, CaCl2, and MgCl2. The effects of temperature and initial DS concentration were investigated on water flux, reverse solute flux, and specific water flux using computational fluid dynamics (CFD). Based on the simulation results, the highest water flux (18 L/m2/h for DI water and 5 L/m2/h for the hydrometallurgical effluent) and lowest reverse solute flux (consistently below 0.3 mol/m2/h) were obtained when MgCl2 was used as the DS. The effect of solute type in the DS on both water recovery yield and purity was in turn studied in the subsequent DFC step, allowing to visualize the solute distribution during the freezing process. HIGHLIGHTS Model development and validation of a forward osmosis-directional freeze crystallization (FO-DFC) desalination process.; MgCl2 exhibited the highest water flux and lowest reverse solute flux in FO.; MgCl2 showed the highest rejection flux among the inorganic salts tested during DFC.; The highest impurity rejection flux rate during ice growth occurred at the solid–liquid interface.;

The use of forward osmosis (FO) for treating biogas slurry was systematically investigated in this study. Membrane performance was investigated with draw solution (DS) concentrations, membrane orientation, solution flow rate and temperature to identify the optimal conditions. All of the parameters including DS concentration, membrane orientation, solution flow rate and temperature had significant influence on membrane performance. Results showed that the optimal operation conditions were DS concentration 2 M, flow rate 1.5 L/min, solution temperature 20°C and FO mode. The recovery rates of total dissolved solids and other substances can reach over 95.6%, no matter how many times concentrated the biogas slurry was. The membrane flux decreased with the increased concentration multiple of biogas slurry. The highest membrane concentration efficiency was about 3 L²/h⋅m²⋅g, when biogas slurry was concentrated between 1.5 and 2 times. FO technology which can improve the application value of biogas slurry as fertilizer effectively was feasible to biogas slurry concentration. [ABSTRACT FROM AUTHOR]